Paging method and system for a radio access network

ABSTRACT

The present invention relates to a paging method and system for a radio access network which provides access to a core network, said system comprising a central network controlling device ( 100 ) for receiving pagings and for distributing said pagings to other network controlling devices ( 5 ) based on a paging information provided to said central network controlling device. Accordingly, while the access network comprises many RNCs and/or RNASs, the information required for paging or mobility management is provided at one place in one location or routing area. Thus, when the core network sends a paging request, the request does not have to be transmitted to many RNCs and/or RNASs and extra paging can be avoided in the access networks. Moreover, a paging coordination is possible despite of the number of different core networks.

FIELD OF THE INVENTION

[0001] The present invention relates to a method and system forproviding a paging function in a RAN (radio access network), e.g. aUTRAN (UMTS Terrestrial Radio Access Network), GERAN (GSM/EDGE RadioAccess Network) or any future potential RAN such as IP-RAN (InternetProtocol RAN), of a cellular network, such as a UMTS (Universal MobileTelecommunications System) network.

BACKGROUND OF THE INVENTION

[0002] Data services of the GSM (Global System for Mobilecommunications) have launched a new era of mobile communications. Theearly analog cellular modems had become unattractive to the market, asthey were slow and unreliable. Now the market for data is moving onwards(more bursty) and upwards (more traffic), and the standardizationinstitutes are working towards higher data rates but more significantlyalso towards packet data services. This will certainly broaden theappeal to end-users because data is routed more efficiently through thenetwork and hence at lower costs, and also access times are reduced.

[0003] The general trend is for data applications to generateincreasingly bursty data streams; this results in inefficient use ofcircuit switched connections. Moreover, fixed networks have seen anenormous growth in data traffic, not at least because of the rise ofInternet access demand, such that it is to be supposed that mobilenetworks will spread as technology and customer expectations move on.The current GSM switch network is based on narrow band ISDN (IntegratedServices Digital Network) circuits, so that the reason for ratelimitations moves from the access network to the core network.

[0004] The new GPRS (General Packet Radio Services) network will offeroperators the ability to charge by the packet, and support data transferacross a high-speed network at up to eight times slot radio interfacecapacity. GPRS introduces two new nodes into the GSM network, a SGSN(Serving GPRS Support Node) and a GGSN (Gateway GPRS Support Node). TheSGSN keeps track of the location of the mobile terminal within itsservice area and sends and receives packets to/from the mobile terminal,passing them on or receiving them from the GGSN. The GGSN then convertsthe GSM packets into other packet protocols (e.g. IP or X.25) and sendsthem out into other networks.

[0005] UMTS will deliver advanced information directly to people andprovide them with access to new and innovative services. It will offermobile personalized communications to the mass market regardless oflocation, network or terminal used. In the basic network architectureaccording to 3GPP Release '99, as defined in the 3GPP technicalspecification TS 23 060 (Version 3.6.0, 2001-01), two or more CN (corenetwork) domains can be connected to one RNC (radio network controller)or a similar unit, e.g. RNAS (Radio access network Access Server), inthe radio access network. Moreover, a UE (user equipment) or a mobileterminal or MS (mobile station) have an independent relation to the two(or more) CN domains, i.e. separate MM (mobility management)connections, such that the two (or more) CNs are “uncoordinated”.

[0006] In the two CNs, switching control is performed by circuitswitched (CS) MSCs (Mobile Switching Centers) and packet switched (PS)3G SGSNs, respectively, which have no interactions with each other. Bothof them have a functionality of their own. When an MS has no CS servicesin use, the MSC sees its MM state “MM idle”. When the MS has no PSservices in use, or it has PDP (packet data protocol) contexts, but ithas not shown any activity for a long time, it is in a PMM (packetmobility management) state “PMM idle” from the 3G SGSN's point of view.When the MS has an ongoing PS or CS connection, it has established anRRC (Radio Resource Control) connection towards the RNC. This means thatthe MS performs either handovers, cell updates or URA (UMTS RegistrationArea) up-dates, depending of the channels it uses and the level ofactivity it has shown lately. From the CNs' point of view, the MS is inthe MM state “MM-connected” (via MSC) or in the PMM state“PMM-connected” (via 3G SGSN). The RNC includes both CRNC-C (ControllingRNC C-plane) and SRNC-C (Serving RNC C-plane) functionalities in thesame physical entity. The CN sees RNCs mapped to LAs (location areas) inthe MSC or to RAs (routing areas) in the 3G SGSN.

[0007] The MS may have only a PS connection in use. Thus, it isPMM-connected in the 3G SGSN and RRC-connected in the RNC, but the MSCsees the MS in state “MM-idle”. If an incoming call arrives at the MSC,the MSC sends a paging message to all RNCs, which serve the LA the MS,has registered to. If there are several RNCs serving the same LA, pagingis sent to the RNC(s) where (an) RRC connection(s) exist(s), but also toRNC(s), which do not know the MS. Thus, unnecessary extra pagings areperformed.

[0008] Furthermore, the MS may have an NRT PDP (Non-Real Time PacketData Protocol) context in use, the RAB (Radio Access Bearer) of whichhas been released due to low level of activity. After that, the MSestablishes a CS call and enters to the MM state “RRC-connected”. Duringthe call, the 3G SGSN may receive data packets related to the NRT PDPcontext. The 3G SGSN then assumes that the MS is in the PMM state“PMM-idle” and sends a paging request to all RNCs, which are mapped toserve the corresponding RA. However, in one of the paged RNCs, the MS'sRRC connection already exists, while all other RNCs perform unnecessaryextra pagings. Thus, signalling load on radio interface paging channelsis significantly increased due to pagings from “unnecessary” cells.

SUMMARY OF THE INVENTION

[0009] It is therefore an object of the present invention to provide apaging method and system for a radio access network (RAN), by means ofwhich the signalling load in the radio interface paging channels can bereduced.

[0010] This object is achieved by a paging system, paging method, andnetwork-controlling device as defined in claims 1, 8 and 16,respectively.

[0011] Accordingly, the paging coordination means are arranged toreceive pagings and to distribute the pagings to other networkcontrolling devices. Thereby, the whole access network is seen as onemapping in the core network. This does not necessarily require changesto standards, but it makes configuration easier. The invention makes aforced location area update concept unnecessary in UMTS. Furthermore,the invention reduces signalling load on radio interface pagingchannels, since a mobile that already has an RRC connection would neverbe paged from “unnecessary” cells.

[0012] Future IP based radio access networks may provide a distributionof functions and a “full-mesh” IPv6 (IP Version 6) network between allbase stations and controllers, which makes this kind of optimization avery attractive feature. Compared to the current UTRAN Release '99 3GPPspecifications, less signalling in lu interfaces and in (radio) pagingchannels (and. also in lub interfaces) can be achieved, wherein a lu isan interface between a RNC and a CN and a lub is an interface between aRNC and a Node B, which is a logical node responsible for radiotransmission/reception in one or more cells to/from the UE. Inparticular, a peculiar ‘forced/prohibited’ LA/RA mechanism as includedin the UTRAN Release'99 specifications for mobiles in connected mode isno longer required.

[0013] The paging coordination means may have storing means for storingreal time information about mobile terminals having a connection to theradio access network. Such real time information may be identificationinformation of the mobile, e.g. the International Mobile SubscriberIdentity or like. Whenever a mobile terminal connects to the radioaccess network, the identification information about the mobile terminalis stored in the storing means and the identification information isremoved from the storing means when the connection to the radio accessnetwork of the mobile terminal is terminated.

[0014] Further, the distribution of pagings is based on a paging messageprovided to the paging coordination means, e.g. the paging message mayinclude information about a location area, a routing area, a cell and/orcell resources, and a real time mapping of mobile terminals beingconnected to the radio access network provided by the storing means.Then, the pagings are directed to mobile terminals located within thearea of the radio access network. Therefore, unnecessary pagings tonetwork elements are avoided, e.g. cells, which are not related to theaddressed mobile terminal.

[0015] Primary, the paging coordination means may be a paging server orcould be implemented in a predetermined radio access network accessserver or a predetermined radio network controller.

[0016] When pagings are routed from packet or circuit switched corenetwork to the paging coordination means within the paging system, thepaging message is provided to the paging coordination means. Based onthe paging message and the information stored by the coordination meansother network controlling devices are determined to which the pagingmessage is to be routed. Thus, the pagings are distributed from thecentral paging coordination means to the determined network controllingdevices.

[0017] In a first embodiment determining other network controllingdevices comprises checking with at least one other paging coordinationfunction of the radio access network whether another paging coordinationfunction has a packet or circuit switched connection to the mobileterminal addressed by the paging and then distributing the pagingmessage to the determined other paging function based on the result ofthe checking step.

[0018] In a second embodiment of the present invention determining othernetwork controlling devices includes checking based on the pagingmessage and the information stored within the coordination functionwhich other network controlling devices the paging message has to berouted to.

[0019] According to the first and second embodiment, while the accessnetwork comprises many RNCs and/or RNASs, the information required forpaging or mobility management (MM) is provided at one place in onelocation area (LA) or routing area (RA). Thus, when the core network(CN) sends a paging request, the request does not have to be transmittedto many RNCs and/or RNASs and extra paging can be avoided in the accessnetworks, e.g. in both GERAN and UTRAN. Moreover, a paging coordinationis possible despite of the number of different CNs, and an opportunityis given to implement UE specific signalling in servers, which are notdependent on the areas.

[0020] In the control plane, the CN may see the access network (e.g. IPRAN) as one address, because all the pagings can be directed to oneserver. Hence, there is no need for area-UE specific signalling elementmappings in the CN. The paging function in the access network will becentralized to one or several servers. This gives the possibility topaging coordination in different access networks (e.g. UTRAN and GERAN).In addition to this, SRNC-C's UE specific functions may be distributedto elements, which have no dependencies to any area. This also gives anopportunity to distribute the load caused by SRNC-C's UE specificfunctions evenly among those elements.

[0021] Further advantageous developments are defined in the dependentclaims.

[0022] In the following, the present invention will be described ingreater detail on the basis of two preferred embodiments with referenceto the accompanying drawings, in which:

[0023]FIG. 1 shows a schematic block diagram of an IP RAN architecturein which the present invention can be implemented;

[0024]FIG. 2 shows an IPRC (IP radio controller) architecture in whichthe present invention can be implemented;

[0025]FIG. 3 shows a schematic block diagram of a RAN access serverdomain with a paging signalling according to a first preferredembodiment of the present invention;

[0026]FIG. 4 shows a schematic block diagram of a RAN access serverdomain with a paging signalling according to a second preferredembodiment of the present invention; and

[0027]FIGS. 5A to 5D show a signalling scenario for a network initiatedpaging operation according to the second preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] In the following, the preferred embodiments of the method andsystem according to the present invention will be described on the basisof a UMTS based radio access system in which independent broadbandwireless access networks are introduced as alternative or additionalradio access technologies for UMTS. The IP RAN is an example for an IPbased RAN for providing access for UEs of multiple radio technologies toUMTS based CNs. Some examples of these radio technologies are GSM, EDGE,WCDMA, and/or WLAN. The first applications to be implemented in IP RANare GERAN (GSM/EDGE RAN), GSM and UTRAN (UMTS Terrestrial Radio AccessNetwork). RAN functionality will be distributed to several servers,which will be connected to an IPv6 based network.

[0029]FIG. 1 shows an IP RAN architecture. According to FIG. 1, thearchitecture can be divided into a control plane (C-plane) functionalityand a user plane (U-plane) functionality, which are both connected to aNode B 20. The Node B 20 is a logical network node responsible fortransmission/reception in one or more radio cells to/from a UE or mobileterminal. Thus, the Node B 20 terminates the lub interface towards theRNC functionality.

[0030] In the user plane, the Node B 20 is connected via an lubUinterface to a U-plane Controlling Radio Network Controller CRNCu 53which has the overall control of the logical resources of its RAN accesspoints. The CRNCu 53 is connected via an lurU interface to a U-planeServing RNC SRNCu 54 with an MDC (Macro Diversity Combining) function.The MDC function is an RNC related user and control plane function,which is adapted to choose the better signal from alternative onesaccording to quality parameters. The lur interface is a logicalinterface between two RNCs. The SRNCu 54 then provides a connection viaa packet switched lu-psU interface to a gateway GW 60 which providesaccess to a core network CN.

[0031] The above-mentioned U-plane elements are connected via respectiveinterfaces Ctrl-C, Ctrl-S and Ctrl-G, respectively, to a C-plane CRNCCRNCc 51 and C-plane SRNC SRNCc 52, respectively, of the C-planefunctionality. The CRNCc 51 and the SRNCc 52 are connected to each othervia an lurC interface.

[0032] In the C-plane, the Node B 20 is connected via an lubC interfaceto the CRNCc 51, and a connection to the core network CN can beestablished via the SRNCc 52 and an lu-psC interface or an lu-cbinterface.

[0033] The functions of the SRNCc 52 and the CRNCc 51 can be gatheredfrom the following tables 1 and 2, respectively. TABLE 1 SRNC-Cfunctions SRNC-C functions UE related function RANAP (Radio AccessNetwork Application Pro- tocol) connection termina- tion RRC connectionman- Establishment, reconfiguration, and release agement or an RRC(Radio Resource Control) connection RAB management Establishment,reconfiguration, and release a RAB (Radio Access Bearer) to the UEAdmission Control Bearer admission control including allocation of airinterface L2 and L1 parameters, decision of radio channel request andmodification QoS (Quality of Service) negotiation across the luinterface Radio Handover (HO) Radio handover control including HOControl decision and resource reservation management Network HO controlincluding relocation of lu connection and L2 processing entity, oranchoring Control and processing of UE measurement Selection of theCRRM, and CRRM enquiry for HO candidate Network handover controlDecision and execution of the relocation of the lu connection Decisionand control of the anchoring of the BTS (Base Transceiver Station)Decision and control of the relocation of the BTS Radio Bearer manage-Radio bearer control including bearer priority ment control Channel typeselection and switching (common-dedicated) Load Control Inquiries fornetwork balance maintenance Temporary Id Control Allocation of GRNTIUser plane control Selection of the GW unit Initialisation andmanagement of the GW connection for the UE User plane control,Initialisation and control of the SRNC-u SRNCu entity for the UEconnections Receive and process quality measurement (FER, Frame ErrorRatio) from the SRNC-u UE Location control func- Selection of the SMLCtions Enquiry to the SMLC for UE positioning Common functions PagingExecution of connected mode paging Relay of idle mode paging message tothe relevant CRNC-C Broadcast, Multicast serv- Relay of the lu-CBmessages to the ice management respective CRNC-C Relay of the NAS(Network Access Server) information from lu interface to the relevantCRNC-C entity Location Measurement Relay LMU (Local Mobile Unit) controlUnits control messages from SMLC to the relevant CRNC-C GW ManagementManagement of the logical resources of the GW (Gate Way), e.g.addresses, etc.

[0034] TABLE 2 CRNC-C functions CRNC-C functions UE related handlingAdmission Control Cell admission control Channel allocation (incl. DFCA)Initial access Selection of the SRNC-c Cell managementAllocation/deallocation of dedicated physical radio channels LoadControl Cell load and congestion control Handover control Handoveralgorithm, pre-processing of the handover measurements Setting thetrigger of the handover measurement controlling RR (Radio cRR functionfor processing of UE Resources) measurement Temporary Id ControlAllocation of Cell RNTI (Radio Network Temporary Identity) Power ControlOpen loop power control (allocation of the initial power) Common PagingExecution of Idle mode paging Cell measurements Collecting cellmeasurements (for CRRM) common and shared Allocation/deallocation ofcommon/shared channel management physical radio channels Control of theCRNC-u entity Broadcasting Information Access stratum info Non accessstratum info Positioning Control of the LMU

[0035] To achieve these functions, the SRNCc 52 is connected via an Lbinterface to a Serving Mobile Location Center SMLC 90 and via an luc2interface to a Common Radio Resources Management CRRM 40 which isconnected via a luc3 interface to an Operation and Maintenance O&Mserver 3 for controlling logical resources owned by the RNCfunctionality. The O&M server 3 is connected via an lubOM interface tothe CRNCc 51 and provides access to an OSS (Operations Support System)via an NWI3 interface. As indicated in FIG. 1, the CRNCc 51 and theSRNCc 52 are connected to a corresponding peer CRNCc 510 and peer SRNCc520, respectively, of the IP RAN.

[0036]FIG. 2 shows an IPRC (IP Radio Controller) architecture, which maybe implemented in the IP RAN. The IPRC consists of many SRNC-Cs (calledRNAS 5) which are independent of any LAs, RAs or other areas, and whichperform only an MS or UE specific signalling.

[0037] The IPRC comprises an O&M server 3 and an RNAS 5 which isconnected via respective signalling connections to a Common ResourceManagement Server (CRMS) 4, to an A Interface Gateway (AGW) 7 forproviding a core network access via the A Interface, to a Radio NetworkGateway (RNGW) 6 which provides a data gateway functionality between anIP-BTS (IP Base Transceiver Station) 10 and a packet switched lu-PS userplane or a circuit switched lu-CS user plane (via an lu InterfaceGateway (IUGW) 8), to a Base Station Gateway (BSGW) 2 of the IP-BTS 10,and to a BTS 1 of the IP-BTS.

[0038] According to the present invention, the paging in the RAN iscoordinated. Thus, unlike in the current architectures (GSM, UTRAN,etc.) where a LA, known by the core network, defines the cells (andradio network controllers/base station controllers or similar units),where paging message should be sent to reach a UE or mobile terminal inidle mode, in this solution, the CN needs to send the paging only to onenode in the RAN and the RAN internally controls the actual paging area.This ‘coordination’ can be implemented in different ways as described inthe first and second preferred embodiments with reference to FIG. 3 andFIGS. 4 and 5A to 5D, respectively.

[0039]FIG. 3 shows an architecture of an RNAS domain and a correspondingpaging signalling according to the first preferred embodiment. Accordingto FIG. 3, a centralized paging server 100 is provided in the RNASdomain, where all paging messages from the CNs are always routed to.This paging server 100 has real-time knowledge of all mobile terminalsor UEs in “RRC connected state” within one RAN. Thus, if a pagingmessage towards such a mobile terminal is received, the paging server100 can forward the message to the correct BSC (Base Station Controller)or RNC or RNAS (etc.), which currently controls the connection of theconcerned mobile terminal.

[0040] The paging server 100 is connected via a signalling connection toa CRS (Cell Resource Server) functionality 11 in the IP-BTS 11. Thissignalling connection is used in the UL (up link) direction for an RNASselection signalling, and in the DL (down link) direction for RRC idlemode pagings. Furthermore, the paging server 100 comprises or hasallocated a database 15 in which mapping information regarding e.g. IMSI(International Mobile Subscriber Identity) to RNAS address mappings andLA/RA/cell-CRS mappings and other mappings required for paging and/ormobility management purposes are stored. The paging server 100 isconnected to the RNAS 5 via another signalling connection through whichcreations and deletions of IMSI to RNAS address associations and othermapping information can be signalled in the UL direction, and throughwhich RRC connected mode pagings can be initiated in the DL direction.Additionally, respective signalling connections between the pagingserver 100 and the CN may be provided to transmit lu-CS and/or lu-PS andA and/or Gb interface control plane signallings and LA/RA specificpaging request. Similar signalling connections may be provided for theRNAS 5 to provide corresponding control plane signalling except forpaging requests. The RNAS 5 may be arranged to forward pagings in cellshared and cell dedicated states via a DL signalling connection to theBase Station Gateway BSGW 2 of the IP-BTS 10. Additionally, GERANpagings in GRA PCH (GERAN RA Paging Channel) states and UTRAN pagings inthe URA PCH (UTRAN RA Paging Channel) states may be forwarded to the CRSfunctionality 11 of the IP-BTS 10 via a corresponding signallingconnection. Packet data can be transmitted via corresponding dataconnections from the CRS functionality 11 and a CGW (Cell Gateway)functionality 12 through the BSGW 2 of the IP-BTS 10 and the RNGW 6 tothe lu-PS user plane of the CN.

[0041] As regards MM signalling functions, a signalling may be performedbetween the BSGW 2 and the RNAS 5 to initiate cell updates, GRA/URAupdates, and/or BTS anchorings and relocations. The BSGW 2 may bearranged to initiate a paging in the GERAN cell shared state and/or apaging in the ready state. Furthermore, a signalling may be performedbetween the RNGW 6 and the RNAS 5 to initiate paging needednotifications in the GRA PCH and URA PCH states. The RNAS 5 may beconnected via respective signalling connections to other RNASs of otherIPRCs to initiate RNAS relocations.

[0042] In general, an RNAS selection needs to be performed when the MSor UE moves from an idle to a connected mode, when the MS or UE performsa location registration or for idle mode paging, and in the connectedmode during The selection can be performed by selecting a default RNASfor the initial access from the MS or UE and for a CN initiated idlemode paging. The default RNAS is associated with the LA/RA, and theanswer for the initial access might be coming from another RNAS. In theconnected mode, the RNAS can be selected based on e.g. the networktopology or load. The CRMS 4 shown in FIG. 2. could be involved in theRNAS selection management.

[0043] The paging server 100 serves as an RNAS receiving idle modepaging requests for a specific LA/RA, and as a default RNAS in aninitial access. As indicated by the arrows in FIG. 3, the paging server100 receives an idle mode paging request from the CN and routes thepaging request to the CRS functionality 11 of the IP-BTS 10. The CRSfunctionality 11 sends an initial access to the paging server 100 whichroutes the initial access to the allocated RNAS, e.g. the RNAS 5, basedon the mapping information in the database 15. The allocated RNAS 5issues an initial access response to the CRS functionality 1. In theconnected mode, paging messages from the CN are routed by the pagingserver 100 to the allocated RNAS 5 which then routes the paging messagesto the BSGW 2. The paging server 100 is informed by the allocated RNAS 5when the RNAS for the RRC connection has changed.

[0044] When an MS establishes an RRC connection in an IP RAN environmentaccording to FIG. 1, its IMSI and SRNC-C UE specific functions serveridentifier are stored to the database 15 at the paging server 100. TheIMSI is provided to the IP RAN by the CN after security procedures havebeen executed. When the MS releases the RRC connection, the MS'sinformation is removed from the database 15. The Paging server 100 hasLA-RA-cell-CRNC-C address mappings stored in the database 15, to be ableto forward pagings to CRNC-Cs.

[0045] When the CN sees the MS in the state “PMM-idle” or “MM-idle”, itsends a paging request towards the paging server 100. The paging server100 checks from its database 15, whether an MS's RRC connection alreadyexists. If there is an existing RRC connection, the paging is forwardedto the corresponding SRNC-C UE specific functional element. Thissituation may occur, if the MS for example has an ongoing PS connectionbut no CS calls. If an RRC connection does not exist, the paging server100 distributes the paging to the CRNC-Cs of the whole LA/RA.

[0046] It is to be noted that the first embodiment shown in FIG. 3 isnot restricted to a single paging server 100, but there can be arrangedmultiple paging servers 100 with a (standard) interface between them.Moreover, the paging server 100 may be arranged as a function inside oneRNAS, wherein the RNAS-RNAS interface function has to be adaptedcorrespondingly so as to support also the paging server signalling. Thedatabase 15 of the paging server 100 can be distributed for the wholeRAN (e.g. IP RAN).

[0047] According to the second preferred embodiment, the coordinationfunctionality can be implemented as a part of a network controller, e.g.a BSC, RNC, RNAS or corresponding controller. When a network controllerreceives a paging message from the CN, it checks from other possiblecontrollers whether they already have a connection for this MS or UE.This could be implemented e.g. so that CN always sends the pagingmessage to only one controller, the message including a list ofcontrollers (or cells) belonging to the LA/RA of the paged MS or UE. Thecontroller receiving the paging message (“first controller”) can nowsend a request for all the other controllers in the list and if one ofthem already has a connection to this MS or UE, forward the pagingmessage from the CN to that controller. If none of the asked controllershave already a connection with the MS or UE, the first controller cancoordinate the idle mode paging either by forwarding the paging messagedirectly to all cells in the LA/RA or by requesting the othercontrollers to page on their cells. This selection depends on the RANarchitecture, e.g. whether there is tight relation between cells andcontrollers or if any controller can access any cell (which may be thecase in the future IP-RAN network shown in FIG. 1).

[0048] Thus, it is enough that the CN sends the paging message to one ofthe RNCs or RNASs together with a list of RNCs or RNASs in therespective RA or LA, and then the RNC or RNAS which received the pagingmessage does the remaining procedures, e.g. checking whether the pagedmobile terminal is active in the cover area of one of other RNCs orRNASs and, if not, executing an idle mode paging in this RA or LA(perhaps with the help of the other RNASs).

[0049]FIG. 4 shows an architecture of an RNAS domain and a correspondingpaging signalling according to the second preferred embodiment. Thearchitecture corresponds to the architecture according to FIG. 3, whilethe paging server 100 has been replaced by a first RNAS 5-1. Thefunction of the elements corresponding to those elements shown in FIG. 3are similar and will therefore not be described again in this secondpreferred embodiment. According to FIG. 4, the first RNAS 5-1 connectedto a CN via an lu control plane for paging requests for a first locationarea LA1, and a second RNAS 5-2 connected to the core network via an lucontrol plane for paging requests for second location areas LA3, LA4 areconnected via a signalling connection. The first RNAS 5-1 has anallocated first database 16-1 and the second RNAS 5-2 has an allocatedsecond database 16-2. In both databases 16-1, 16-2, LA/RA/cell-CRSmapping information is stored. The first RNAS 5-1 receives idle modepaging requests for the first location area LA1 and serves as a defaultRNAS in an initial access. The CGW functionality 12 of the IP-BTS 10 isresponsible for the cells belonging to the first location area LA1.

[0050] As indicated by the arrows in FIG. 4, an idle mode paging requestis issued by the CN to the default first RNAS 5-1 which routes the idlemode page request to the CRS functionality 11 of the IP-BTS 10. The CRSfunctionality 11 responds to the first RNAS 5-1 with an initial accessmessage which is routed by the first RNAS 5-1 based on the mappinginformation of the first database 16-1 to a selected or allocated RNAS,e.g. the second RNAS 5-2. In response thereto, the second RNAS 5-2issues a response message to the CRS functionality 11, and the RRCconnection can be established. In the connected mode, pagings are alsorouted from the core network via the default first RNAS 5-1 to the CRSfunctionality 11 of the IP-BTS 10.

[0051] The access network architecture may differ from the architecturesshown in FIG. 3 and 4. In particular, the access network could beimplemented without RNCs or RNASs. Then, the lu interface is connecteddirectly to the base station 10.

[0052] In the following, an idle paging scenario is described in anUTRAN environment with reference to FIGS. 5A to 5D, wherein a UE 17having a connection to a first core network CN1 and being in an idlemode towards a second core network CN 2 is paged from the second corenetwork CN 2.

[0053] According to FIG. 5A, a first and a second Node B 20-1, 20-2having a BTS functionality in the UTRAN environment are connected via afirst RNC 50-1 to the first and second core networks CN1, CN2.Similarly, a third and a fourth Node B 20-3, 20-4 also having a BTSfunctionality in the UTRAN environment are connected via a second RNC50-2 to the first and second core networks CN1, CN2. In the situationshown in FIG. 5A, the UE 17 has a connection established via the secondNode B 20-2 and the first RNC 50-1 to the first core network CN1.

[0054] Then, as indicated in FIG. 5B, the second core network CN2 issuesan idle mode paging request, including an identification UE-id of the UE17 and an indication that the location area LA1 is covered by both thefirst and second RNC 50-1, 50-2. The second core network CN2 may selectany RNC in the location area LA1 as a target for the paging message. Itdoes not know that the UE 17 has an existing connection in the first RNC50-1. In the present example, the second core network CN2 selects thesecond RNC 50-2.

[0055] According to FIG. 5C, the selected second RNC 50-2 checks whetherany other RNC in the location area LA1 has a connection established forthe concerned UE 17. In particular, the second RNC 50-2 may issue arequest based on a mapping information stored at the second RNC 50-2 tothe concerned other RNCs asking whether the other RNCs in the locationarea LA1 have this UE 17 registered as connected and including theidentification UE-id and the paging message. In response to thisrequest, the first RNC 50-1 having a connection established for theconcerned UE 17 answers to the second RNC 50-2 and continues the pagingprocedure using the existing dedicated RRC connection. As indicated inFIG. 5D, the first RNC 50-1 sends a corresponding acknowledgement (“Yes,I will forward the page to him!”) to the second RNC 50-2. Thereby,unnecessary paging signallings from the second core network CN2 to theother concerned RNCs in the location area LA1 can be prevented to reducesignalling load.

[0056] It is noted that the present invention can be applied to anyaccess network structure having a paging function for paging a terminaldevice from a cellular network. The description of the preferredembodiment is only intended to illustrate the present invention. Thepreferred embodiment may thus be modified within the scope of theattached claims.

1. A paging system for a radio access network which provides access toat least one core network, said system comprising a paging coordinationmeans (100, 5-1, 50-2) arranged to receive pagings, to check forexisting connections, and to distribute said pagings to other networkcontrolling devices (5, 5-2; 50-1) based on a paging message provided tosaid paging coordination means (100, 5-1, 50-2) and the checking result.2. A system according to claim 1, wherein said pagings are directed tomobile terminals (17) located within the area of said radio accessnetwork.
 3. A system according to claims 1 or 2, wherein said pagingcoordination means (100, 5-1, 50-2) is a paging server (100), apredetermined radio access network access server (5-1), or apredetermined radio network controller (50-2).
 4. A system according toclaim 3, wherein said paging coordination means (100, 5-1, 50-2) hasstoring means for storing real time information about mobile terminalshaving a connection to said radio access network.
 5. A system accordingto claim 4, wherein said real time information is an identificationinformation of said mobile (17).
 6. A system according to claim 5,wherein said identification information is an International MobileSubscriber Identity.
 7. A system according to any one of the proceedingclaims, wherein said paging message includes information about alocation area, a routing area, a cell and/or cell resources.
 8. A systemaccording to any one of the proceeding claims, wherein said radio accessnetwork provides access to packet switched and circuit switched corenetworks and said paging coordination means is arranged to receivepagings from both core networks.
 9. A system according to any one of theproceeding claims, wherein said radio access network comprises UTRAN,GERAN and/or other radio access networks.
 10. A method of paging in aradio access network which provides access to at least one core network(CN; CN1, CN2), said method comprising the steps of: a) routing pagingsfrom said core network to a paging coordination function (100; 5-1;50-2); b) providing a paging message to said paging coordinationfunction (100; 5-1; 50-2); c) determining other network controllingdevices (5; 5-2; 50-1) to which said paging message is to be routed,based on said paging message, and an information about existingconnections obtained by said coordination function (100; 5-1, 50-2); andd) distributing said pagings from said paging coordination function(100; 5-1; 50-2) to said determined network controlling devices (5; 5-2;50-1).
 11. A method according to claim 10, wherein said paging messageincludes information about a location area, a routing area, a celland/or cell resources.
 12. A method according to claim 10 or 11,comprising further the steps of: a) storing an identificationinformation about a mobile terminal being connected to said radio accessnetwork in storing means by said paging coordination function (100; 5-1;50-2); and b) removing said identification information about said mobileterminal from said storing means when said connection to said radioaccess network of said mobile terminal is terminated.
 13. A methodaccording to claim 12, wherein said storing means are arranged toprovide a real time mapping of mobile terminals being connected to saidradio access network.
 14. A method according to claim 12 or 13, whereinsaid information comprises an identification information of said mobilebeing connected to said radio access network.
 15. A method according toclaim 14, wherein said identification information is an InternationalMobile Subscriber Identity.
 16. A method according to anyone of thepreceding claims 10 to 15, wherein said determining comprises the steps:a) checking with at least one other paging coordination function (50-1)of said radio access network whether another paging coordinationfunction (50-1) has a connection to said mobile terminal (17) addressedby said paging; and b) distributing said paging message to saiddetermined other paging function (50-1) based on the result of saidchecking step.
 17. A method according to, anyone of the preceding claims10 to 15, wherein said determining comprises the step: checking based onsaid paging message and said information stored within said coordinationfunction (100) which other network controlling devices (5) said pagingmessage has to be routed to.
 18. A method according to anyone of theclaims 10 to 17, wherein said radio access network provides access topacket switched and circuit switched core networks and said pagingcoordination means is arranged to receive pagings from both corenetworks.
 19. A method according to anyone of the claims 10 to 18,wherein said radio acces network comprises UTRAN, GERAN and/or otherradio access networks.
 20. A network controlling device for a radioaccess network which provides access to at least one core network (CN;CN1, CN2), said device (100; 5-1, 50-2) comprising: a) receiving meansfor receiving a paging message directed to a mobile terminal (17); b)storing means (15; 16-1, 16-2) for storing an information about mobileterminals being connected to said radio access network; and c) pagingcontrol means for performing control so as to distribute said pagingmessage to other network controlling devices (5; 5-2; 50-1) based on achecking function checking other network controlling devices (5; 5-2;50-1) having a connection to said paged mobile terminal (17) based onsaid stored information.
 21. A device according to claim 20, whereinsaid network controlling device is a paging server (100), a radio accessnetwork access server (5-1), or a radio network controller (50-2). 22.(New) A paging system for a radio access network which provides accessto at least one core network, said system comprising a pagingcoordination means arranged to receive pagings, to check for existingconnections, and to distribute said pagings to other network controllingdevices based on a paging message provided to said paging coordinationmeans and the checking result.
 23. (New) A system according to claim 22,wherein said pagings are directed to mobile terminals located within thearea of said radio access network.
 24. (New) A system according to claim22, wherein said paging coordination means is a paging server, apredetermined radio access network access server, or a predeterminedradio network controller.
 25. (New) A system according to claim 24,wherein said paging coordination means has storing means for storingreal time information about mobile terminals having a connection to saidradio access network.
 26. (New) A system according to claim 25, whereinsaid real time information is an identification information of saidmobile.
 27. (New) A system according to claim 24, wherein saididentification information is an International Mobile SubscriberIdentity.
 28. (New) A system according to claim 22, wherein said pagingmessage includes information about a location area, a routing area, acell and/or cell resources.
 29. (New) A system according to claim 22,wherein said radio access network provides access to packet switched andcircuit switched core networks and said paging coordination means isarranged to receive pagings from both core networks.
 30. (New) A systemaccording to claim 22, wherein said radio access network comprisesUTRAN, GERAN and/or other radio access networks.
 31. (New) A method ofpaging in a radio access network which provides access to at least onecore network, said method comprising the steps of: a) routing pagingsfrom said core network to a paging coordination function; b) providing apaging message to said paging coordination function; c) determiningother network controlling devices to which said paging message is to berouted based on said paging message, and an information about existingconnections obtained by said coordination function; and c) distributingsaid pagings form said paging coordination function to said determinednetwork controlling devices.
 32. (New) A method according to claim 31,wherein said paging message includes information about a location area,a routing area, a cell and/or cell resources.
 33. (New) A methodaccording to claim 31, comprising further the steps of: a) storing anidentification information about a mobile terminal being connected tosaid radio access network in storing means by said paging coordinationfunction; and b) removing said identification information about saidmobile terminal from said storing means when said connection to saidradio access network of said mobile terminal is terminated.
 34. (New) Amethod according to claim 33, wherein said storing means are arranged toprovide a real time mapping of mobile terminals being connected to saidradio access network.
 35. (New) A method according to claim 33, whereinsaid information comprises an identification information of said mobilebeing connected to said radio access network.
 36. (New) A methodaccording to claim 35, wherein said identification information is anInternational Mobile Subscriber Identity.
 37. (New) A method accordingto claim 31, wherein said determining comprises the steps: a) checkingwith at least one other paging coordination function of said radioaccess network whether another paging coordination function has aconnection to said mobile terminal addressed by said paging; and b)distributing said paging message to said determined other pagingfunction based on the result of said checking step.
 38. (New) A methodaccording to claim 31, wherein said determining comprises the step:checking based on said paging message and said information stored withinsaid coordination function which other network controlling devices saidpaging message has to be routed to.
 39. (New) A method according toclaim 31, wherein said radio access network provides access to packetswitched and circuit switched core networks and said paging coordinationmeans is arranged to receive pagings from both core networks.
 40. (New)A method according to claim 31, wherein said radio access networkcomprises UTRAN, GERAN and/or other radio access networks.
 41. (New) Anetwork controlling device for a radio access network which providesaccess to at least one core network, said device comprising: a)receiving means for receiving a paging message directed to a mobileterminal; b) storing means for storing an information about mobileterminals being connected to said radio access network; and c) pagingcontrol means for performing control so as to distribute said pagingmessage to other network controlling devices based on a checkingfunction checking other network controlling devices having a connectionto said paged mobile terminal base don said stored information. 42.(New) A device according to claim 41, wherein said network controllingdevice is a paging server, a radio access network access server, or aradio network controller.